The purpose of this study is to determine whether vitamin E or donepezil hydrochloride (Aricept) can delay a diagnosis of Alzheimer's Disease in some people experiencing mild memory problems (referred to in this study as "mild cognitive impairment"). This study will be conducted at sixty to eighty clinical sites in the United States and Canada. Each site will enroll 12-36 subjects, for a total of 720 subjects throughout all of the sites.